replaced the water pump on my 05 3.7L WK about two years ago at 70,000 miles. The bearings had begun to fail and I had a chattering at idle from the pump pulley. I installed a brand new Mopar pump from the dealer. I topped off any coolant lost in changing the pump with a 50/50 mixture of Prestone and distilled water. I probably added about a gallon of the Prestone mix. (Note that I was lazy and didn't drain the coolant, I just pulled the pump and let the coolant spill out into my catch basin).

Now only two years and 35,000 miles later, the new pump is leaking! The bearings seam fine but I am loosing fluid overnight after it cools down. I've never seen anything like it, it only leaks when the outside temp goes below freezing. Once you start it up and get up to operating temp, the leak goes away! It appeared to be leaking past the water pump gasket/seal. I've just installed another new OEM pump and topped off with 50/50 Prestone again.

Now I've noticed that Jeep cautions against mixing "non-hoat" anti-freeze with the OEM "hoat" anti-freeze. My question is did my mixing 50/50 Prestone with the factory coolant, lead to the new pump/gasket failing in just two years??

Does the Prestone attack the rubber water pump gasket/seal?? I'm thinking I should do a coolant flush and re-fill with OEM coolant.

Personally I just think the pumps are JUNK. I had my first pump go out, literally blowing coolant all over the road, at 43k (untouched OEM only fluid) and just replaced another 2 weeks ago with just over 75k miles (again, untouched OEM only fluid).
So, I'm on my 3rd OEM pump at just over 75k miles....with OEM fluid.